High-Throughput Analysis of Microdissected Tissue Samples - High-Throughput Image Reconstruction and Analysis - page 245

Technologies GmbH) based on microdissection with a UV laser that generates
photonic pressure and catapults the dissected cells into a microcentrifuge tube
cap [30, 31]. This system provides a noncontact method, differing from LCM in
this regard [Figure 11.2(b)]. PALM is partially automated but is also operator-
dependent since the researcher needs to identify and microscopically select the
cells for dissection. A similar cutting laser microdissection is the Leica LMD (Leica
Microsystems), which differs from the PALM in that the dissected cells fall by
gravity into a tube instead of being catapulted by pressure [32] [Figure 11.2(c)].
Finally, another UV laser--based system is the MMI Cellcut system (Molecular
Machines & Industries) [33] whose main advantage is avoidance of contamination
via minimizing environmental contact during dissection. It has been reported that
UV-induced biomolecule damage can occur in cells lying directly under the laser
cutting path and the damage can be significant if the cut region is large in relation
to the microdissected area [34].
11.2.4.4 Combined Laser Capture-Cutting Systems (IR and UV Lasers)
Molecular Devices, Inc., offers two new semi-automated instruments that combine
infrared and UV lasers, Veritas and Arcturus XT. Veritas is a closed system with
improved imaging software. More recently, the Arcturus XT was developed, adding
additional contrast phase illumination and fluorescence capabilities along with
the dual laser approach. Overall, the enhanced optics, dissection flexibility, and
improved software all facilitate more rapid and precise dissections.
11.2.4.5 Ultrasonic-Based Microdissection
This is a recently developed approach in which microdissection is performed using
ultrasonic vibration as a cutting system [35]. A piezoelectric actuator generates a
high frequency and low amplitude vibration (approximately 16 to 50 kHz, and
0to3mm) that cuts the tissue [35]. Preliminary data shows that the method is
reliable and the biomolecules in the tissue are not damaged during the dissection
process [35].
11.2.4.6 High Throughput, Operator-Independent Microdissection
(Expression Laser Microdissection, xMD)
One of the major challenges in the microdissecion field is that all of the laser-
based techniques, although they have contributed greatly to the field of molecular
pathology, are operator-dependent and thus somewhat laborious to utilize. The
rate-limiting step in most dissection studies is the laser operator who must carefully
select the cells for procurement one by one, a process that can often require days or
weeks of effort to procure enough cells for analysis. Therefore, new microdissection
systems are needed, especially those that increase the speed of dissection and thus
decrease operator time. More efficient yields of dissected cells are particularly
relevant for proteomics since there is no tool available for protein amplification.
In 2004 expression microdissection (xMD) was developed by investigators at
the NIH. The method is a high throughput process for procuring specific cell